The present invention relates generally to methods for detecting malignant tissue and more particularly to a method for detecting malignant tissue using time-resolved fluorescence spectroscopy.
As can readily be appreciated, the detection of malignant (i.e. cancerous) tissue is often a prerequisite to its treatment.
In U.S. Pat. No. 4,930,516, which is issued on Jun. 5, 1990 with Alfaro et el. as inventors, a method and an apparatus for detecting the presence of cancerous tissue using visible luminescence are described. According to the teachings of this patent, the tissue to be examined is excited with a beam of monochromatic light that causes the tissue to fluoresce over a spectrum of wavelengths. The intensity at which the excited tissue fluoresces can be measured either over a spectrum or at a predetermined number of preselected wavelengths. By determining the waylengths at which maximum intensities are attained for the tissue in question and by comparing these peak wavelengths, either visually or electronically, to the peak wavelengths derived from a known non-cancerous tissue, or by comparing the spectrum of the excited tissue with the spectrum of a known noncancerous tissue one can determine the carcinomatoid status of the tissue in question. The invention is based on the discovery that the visible luminescence spectra for cancerous and non-cancerous tissue are substantially different and that the differences are such that visible luminescence from tissue can be used to detect the presence of cancer.
In U.S. Pat. No. 5,042,494, which issued on Aug. 27, 1991 with Alfaro as inventor, a method and an apparatus for detecting the presence of cancerous tissue using native visible luminescence are described. The tissue to be examined is excited with a beam of monochromatic light that causes the tissue to fluoresce over a spectrum of wavelengths. The intensity at which the excited tissue fluoresces can be measured either over a spectrum or at a predetermined number of preselected wavelengths. By determining the wavelengths at which maximum intensities are attained for the tissue in question and by comparing these peak wavelengths, either visually or electronically, to the peak wavelengths derived from a known non-cancerous tissue, or by comparing the luminescence spectrum of the excited tissue with the luminescence spectrum of a known noncancerous tissue and/or known cancerous tissue or the excitation spectrum of the excited tissue with the excitation spectra of known cancerous and/or known non-cancerous tissues one can determine the carcinomatoid status of the tissue in question. Once it has been determined that the tissue is cancerous, it may be destroyed by ablation by exposing it to a beam of light from a high power laser. The invention is based on the discovery that the visible luminescence spectra for cancerous and non-cancerous tissues are substantially different and that the differences are such that visible luminescence from the tissue can be used to detect the presence of cancer and also on the discovery that the spectral profiles of excitation spectra are similarly different.
In Japanese Pat. No. Hei2-22331, which was laid open on Jul. 13, 1983 and which issued on May 18, 1990 with Nishizaka et al. as inventors, a method and a device for detecting abnormal tissue, such as cancerous tissue, by spectroanalysis are described. The method of the present Invention comprises the steps of directing a laser beam onto various samples, analyzing the spontaneous emission caused in the samples, and analyzing the change in the physical characteristics of the samples. Various laser beams, such as the single wave or tunable laser pulse or continuous-mode oscillation laser, are applicable for the excitation of the sample cells. In addition, various spectra are used, such as the wave spectrum, time resolved spectrum, fluorescence spectrum, Raman spectrum and polarized light spectrum. The use of a single spectrum as well as a combination of two or more of the spectra is possible.
In copending and commonly assigned U.S. patent application Ser. No. 07/468,633, filed on Jan. 22, 1990 with Alfano et el. as inventors, a method and an apparatus for distinguishing cancerous tumor tissue from benign tumor tissue, benign tissue and normal tissue using native fluorescence are described. The tissue to be examined is excited with a beam of monochromatic light at about 300 nm. The intensity of the native fluorescence emitted from the tissue is measured at about 340 and 440 nm. The ratio of the two intensities is then calculated and used as a basis for determining if the tissue is cancerous as opposed to benign or normal. The invention is based on the discovery that when cancerous tissue is excited with monochromatic light at about 300 nm, the native fluorescence spectrum over the region from about 320 nm to 600 nm is substantially different from the native fluorescence spectrum that would result if the tissue were either benign or normal. The technique is useful in vivo and in vitro testing of human as well as animal tissue.
In U.S. Pat. No. 4,957,114, which issued on Sep. 18, 1990 with Zeng et el. as inventors, a diagnostic apparatus for intrinsic fluorescence of malignant tumors and a method for using the apparatus for diagnosis are described. The apparatus employs an ultraviolet light source with an emitting waveband of 3000A-4000A. Light from the light source is transmitted through a bundle of quartz optic fibers to the surface of the tumor, whether benign or malignant, to stimulate it, which then generates a specific intrinsic fluorescence spectrum. The intrinsic fluorescence spectrum reflected from the surface of the tumor is transmitted by a second bundle of glass fibers placed near it to a color resolution means, then processed by a scanning means and a circuit means, and displayed recorded by a display recording means. The display may be a graphic presentation of the intrinsic fluorescence spectrum of the tumor that is tested. If the graphic presentation displayed includes a single peak within the range of the blue color band, it indicates that the tumor being tested is bengin. If however, a second peak appears within the range of the red color band of the graphic presentation it is a characteristic peak of malignancy, indicating the existence of a malignant tumor. The presence of the red color can be established by eye rather than a complex resolution system.
In copending and commonly assigned U.S. patent application Ser. No. 07/651,449 filed on Feb. 7, 1991 with Alfano et el. inventors, a method for determining if a tissue is a malignant tumor tissue, a benign tumor tissue, or a benign or normal tissue using Raman spectroscopy is described. The method is based on the discovery that, when irradiated with a beam of infrared, monochromatic light, malignant tumor tissue, benign tumor tissue, and normal or benign tissue produce distinguishable Raman spectra. For human breast tissue, some salient differences in the respective Raman spectra are the presence of four Raman bands at a Raman shift of about 1079, 1300, 1445 and 1659 cm.sup.-1 for normal or benign tissue, the presence of three Raman bands at a Raman shift of about 1240, 1445 and 1659 cm.sup.-1 for benign tumor tissue, and the presence of two Raman bands at a Raman shift of about 1445 and 1859 cm.sup.-1 for malignant tumor tissue. In addition, it was discovered that for human breast tissue the ratio of intensities of the Raman bands at a Raman shift of about 1445 and 1659 cm.sup.-1 is about 1.25 for normal or benign tissue, about 0.93 for benign tumor tissue, and about 0.87 for malignant tumor tissue.